9 Things That Can Happen to Your Body When You Get Too Much Sleep

Lots of us struggle to get enough shut-eye—but too much sleep isn't good for you, either. Here's why it's bad to OD on z's, and how to find the sandman's sweet spot.

You’re at greater risk for heart disease and stroke

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The negative health effects of too little sleep are well-documented, but what happens from too much sleep is less clear. The National Sleep Foundation recommends that the average adult get 7 to 9 hours of sleep. But what if your body craves more sleep: Can you get too much? A growing body of research connects oversleeping with bad health outcomes. “Oversleeping is not harmful in and of itself, but it is a sign that you may be sleeping ineffectively, or that there is another problem requiring more sleep,” says Carl Bazil, MD, director of the division of sleep and epilepsy at New York-Presbyterian/Columbia University Medical Center. “There are also otherwise normal people who are ‘long sleepers’—they function perfectly well if they get 9 or 10 hours but are sleepy on less. It’s still important, however, to check for other possibilities.” One concerning problem linked with long sleep is cardiovascular disease. Researchers from the Chicago School of Medicine found that people who sleep more than 8 hours per night are twice as likely to have angina (chest pain) and 10 percent more likely to have coronary heart disease. The large Nurse’s Health Study found the risk of heart disease was even larger, with a 38 percent greater chance in long sleepers. The risk of stroke also goes up: One study from the United Kingdom showed a 46 percent greater chance of stroke in long sleepers, even after adjusting for other risk factors. Oppositely, here’s what happens when you don’t get enough sleep.

You might not be sleeping well

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One theory about why too much sleep is linked with other health problems is that your time in bed is disrupted, so you’re not actually getting good rest. “Those with untreated sleep apnea [a common breathing problem] have a tendency to oversleep, and we know that undiagnosed and untreated sleep apnea leads to both heart disease and stroke,” says Michael J. Breus, PhD, a clinical psychologist known as The Sleep Doctor. He says that other problems like stomach upset or hot flashes could also be the cause of poor sleep, or your environment might not be dark or quiet enough. Even teeth grinding can cause you not to sleep as well. If you feel that you’re still sleepy even though you’ve been in bed a long time, talk to your doctor to tease out the cause. These are the signs of sleep apnea you need to know.